Epinephrine induced cardiac dysrhythmias and cardiovascular responses during halothane anesthesia for 70 pediatric tonsillectomy cases were observed at Taegu Catholic Medical College from January to July, 1991 We have evaluated the frequencies of cardiac arrhythmia, and the changes of heart rate and blood pressure according to the administration of epinephrine for the purpase of hemostasis on the operating fields. All patients were divided into 3 groups as follows: Group I; Epinephrine used under halothane anesthesia(n=30). Group II; Epinephrine used under halothane anesthesia with fentanyl(n=20). Group III; Epinephrine used under halothane anesthesia with fentanyl, but shut-off the halothane inhalation briefly(n=20). The results were as follows: l) Systolic blood pressure, Increases of systolic blood pressure were observed in all groups compared with pre-injection state and there were statistical significances in group L 2) Heart rate; Decreases of heart rate were observed in group III compared with pre-injection state and there were statistical significances in group III compared with group I. 3) Dysrhythmias; Most childrens electrocardiograms revealed the sinus rhythms except only 4 cases of premature ventricular contraction and 2 cases of nodal rhythm. These benign dysrhythmias were restored to normal sinus rhythms immediately after administration of small doses of lidocaine & 100% oxygen and simultaneously shut-off the inhalation of halothane.